1. 1Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 1 Runcom Preamble vs. Phillips Proposed Sequences IEEE P802.22 Wireless RANs Date: 2007-04-18 Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org. patcom@iee.org

2. 2Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 2 Runcom Preamble vs. Phillips Proposed Sequences

3. 3Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 3 Introduction Preamble sequences have to satisfy the following conditions: 1.Low PAPR 2.The classic PN properties: Which means, that the autocorrelation of each sequence should have one peak value and the cross-correlation of two sequences should be approximately zero.

4. 4Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 4 PAPR Our simulations show, that the PAPR of Phillips sequences is about 0.5 dB worse about then the PAPR of the 802.16. 802.16 PAPR = 4.2 – 4.7 dB Phillips PAPR = 4.74 to 5.07 dB

5. 5Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 5 Frequency shift degradation influence on time domain correlation (no frequency shift) Sequence without shift

6. 6Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 6 Frequency shift degradation influence on time domain correlation (1 bin shift) Sequence with one bin shift

7. 7Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 7 Frequency shift degradation influence on time domain correlation (10 bin shift) Not detectable at all

8. 8Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 8 1 Bin shifted sequence vs. sequence without shift 5 dB worse than the one without frequency shift.

9. 9Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 9 1 Bin shifted sequence vs. sequence without shift

10. 10Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 10 We have received a set of 114 preamble sequences from Phillips for evaluation. The 57 of the sequences were made from a single sequence generator with cycle of 511 samples. Many sequences suffer from cross-correlation that is nearly identical to the auto-correlation of one of them. Frequency Domain Correlation Properties

11. 11Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 11 Auto-correlation properties ( Phillips sequences ) As we from the figures above, the sequences does NOT satisfy the PN sequence condition on Slide 3.

12. 12Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 12 Auto-correlation properties ( WiMax sequences ) As we from the figures above, the 802.16 sequences have almost perfect autocorrelation property.

13. 13Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 13 The figure shows the autocorrelation of sequence #24 vs. the cross-correlation with sequences #6. Note that these are almost identical modulo a shift of 2 samples. Cross-correlation vs. Auto-correlation ( Phillips sequences ) Autocorrelation of sequence #24 vs. Cross-correlation between sequences #24 and #6

14. 14Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 14 This figure shows the autocorrelation for 802.16 sequence #1 vs. cross- correlation with sequences #7. Sequence Detection ( 802.16 sequences ) Autocorrelation of sequence #1 vs. Cross-correlation between sequences #1 and #7

15. 15Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 15 Remarks The time correlation for PN detection, as it has been proposed in Phillips's presentation, requires huge complex multiplications and memory usage. Frequency correlation, for our opinion, is far better than proposed one. Therefore, frequency correlation properties should satisfy the condition on Slide 3 for all lags and not for the limited part of the sequence. We dont agree with assumption, that all synchronizations are made in super-frame and the frame is perfectly synchronized. This issue has to be studied more carefully. There is possibility, that from frame to frame the symbol could go out of synchronization. In this case, the time correlation will severely degrade. (Our simulations shows 5-23.8 dB degradation for 1-10 bins shift accordingly) We strongly recommend to seek other PN sequences which meet the conditions.

16. 16Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 16 Conclusions Our examinations show that the PAPR of the proposed is not better than WiMaxs. The correlation properties exhibit significant flaws. Perhaps the most serious flaw is the auto-correlation/ cross-correlation properties. We recommend following actions: Seek other PN sequences which meet the conditions. Perform better simulations with consideration of all possible scenarios.